Process for developing photographic elements

ABSTRACT

Improved processes are disclosed for providing an image record in a photographic element which comprises a support and at least one layer thereon containing a silver halide emulsion which has associated therewith an image dye-providing color coupler. Generally, the process comprises the improvement wherein a photographic element containing a silver halide and an imagewise distribution of metallic silver is contacted in the presence of a color-developing agent with an amplifier composition which contains a cobalt (III) complex.

United States Patent 1191 Travis PROCESS FOR DEVELOPING PHOTOGRAPHICELEMENTS [75] Inventor:

[73] Assignee: Eastman Kodak Company,

Rochester, N.Y.

22 Filed: May 23,1972

21 Appl. No.: 256,071

William Blair Travis, Fairport, NY.

[52] US. Cl. 96/55, 96/27 R, 96/50 R, 96/66 R, 96/66.3, 96/100,GO3c/1/40 [58] Field of Search 96/48 R, 50 R, 66, 96/66.3, 27, 29 D,100, 55

[56] References Cited UNITED STATES PATENTS 3,701,660 10/1972 Pratt eta]. 96/48 R FOREIGN PATENTS OR APPLICATIONS 239,875 Great Britain Oct.16, 1973 777,635 6/1957 Great Britain Primary Examiner-Norman G. TorchinAssistant Examiner-Richard L. Schilling Attorney-Robert W. Hampton eta1.

[ 5 7] ABSTRACT 40 Claims, 4 Drawing Figures DEA/S/TY ame PAIENIEDnm 16I975 SHEET 2 0F 2 wvw PROCESS FOR DEVELOPING PHOTOGRAPHIC ELEMENTS Thisinvention relates to a process for developing photographic elementswhich comprise layer units containing imagewise-exposed silver halidehaving associated therewith a photographic color coupler. In one aspect,this invention relates to a process for developing a visible imagerecord in photographic elements which comprise color-providing layerunits containing a low silver coverage. In another aspect, thisinvention relates to a continuous process for developingimagewiseexposed photographic elements which comprise at least twocolor-providing layer units wherein, if desired, at least a portion ofthe image dye can be produced under roomlight conditions.

It is known in the art to process photographic elements comprisingsilver halide emulsions and photographic color couplers wherein saidelement is contacted with an aromatic primary amino silver halidedeveloping agent to form silver and dye. Other references such as U.S.Pat. Nos. 2,750,292 by Dippel et al issued June 12, 1956, and U.S. Pat.No. 2,173,739 by Weber issued Sept. 19, 1939, disclose processes forintensifying an image formed by a light-sensitive metal salt by treatingthe imagewise-exposed element with a colordeveloping agent and aphotographic color coupler in the presence of developable silver halideor with a physical developing agent to form an image dye in the areas ofdevelopment. More recently, British Patent 1,268,126 also disclosed aprocess of intensifying a silver image by treating a developed silverimage with solutions containing peroxy compounds and color developers.

However, several of the methods available in the art do not appear to bepractical on a commercial basis due to several problems inherent in thesystem, including instability of the solutions used to intensify theimage record recorded by the light-sensitive metal salt. Where thesilver is bleached and redevelopment takes place with a color developerand a coupler, the bleaching step is quite critical as the latent imagecan be lost where bleaching has completely converted a silver grain tosilver halide and, moreover, solutions containing both color-developingagent and color coupler are prone to formation of dye in the baththrough aerial oxidation of the developer, etc., causing dyecontamination, and also these systems are generally limited to one-colorsystems. Where a physical developing agent is used in combination with acolor coupler and a colordeveloping agent, the processing baths areoften autocatalytic since the reaction products of the redox reactionwith the physical developer provide a catalyst for more redox reactions.

New processes for developing and amplifying an image record recorded ina light-sensitive metal salt are disclosed in Bissonette, U.S. Ser. No.189,289, entitled Image-Forming Processes and Compositions filed Oct.14, 1971, and incorporated herein by reference. In one embodiment, theprocess disclosed relates to image formation in photographic elementscomprising color-providing layer units containing a silver halideemulsion having associated therewith a color coupler. In the process,the photographic element is contacted with a photographiccolor-developing agent and a metal complex, such as a cobalt(lII)complex having a coordination number of 6, until the desired dye densityis obtained. The cobalt complex is apparently reduced to cobalt (ll),which isnot a catalyst for further redox reaction, in the presence ofsilver, and the color developer is oxidized whereby it can react withthe color coupler in each respective layer unit to form the desiredimage dye. Certain preferred photographic elements which can beprocessed by this procedure are described in Bissonette, U.S. Ser. No.256,072, entitled Photographic Elements filed on even date herewith andincorporated herein by reference.

I have now found an improved procedure for processing photographicelements which comprise a support and at least one layer thereoncontaining a silver halide emulsion which has associated therewith animage dye-providing color coupler. Generally, this process comprises theimprovement in forming a visible image record in a photographic elementwherein the photographic element comprising both silver halide and animagewise distribution of metallic silver (i.e., a photographic elementwhich has not been fixed to remove the undeveloped silver halide) iscontacted in the presence of a color-developing agent with an amplifiercomposition which represses substantially additional net silverdevelopment and which contains a cobalt (lIl) complex having acoordination number of 6, wherein said contact is maintained underconditions which reduce cobalt(Ill) to cobalt(ll) and in turn oxidizesaid color-developing agent, whereby image dye is formed from the colorcoupler in said photographic element and said oxidized color-developingagent. The metallic silver in the photographic element can be latentimage silver and is preferably metallic silver formed in a reaction witha silver halide reducing agent such as by development of a latent imagewith a silver halide developer. While latent image silver can be used asa catalyst in the amplification, dye production can generally beexpedited by providing larger catalytic surfaces as produced in silverhalide development. The color-developing agent can be present in theamplification bath but is preferably imbibed into the element prior tocontact with the amplifier composition. In certain embodiments, themetallic silver is provided, when larger than latent image quantitiesare desired, in a bath which contains a color-developing agent, such asan aromatic primary amino compound, which can reduce silver halide tosilver and in turn produce image dye through its reaction products. Incertain preferred embodiments, metallic silver is produced,before-amplification, in a bath in the presence of a black-and-whitedeveloping agent and a color-developing agent wherein improved resultswith respect to shortened process time and matched developability of thevarious layers in a multilayer photographic element can be obtained.

In one highly preferred embodiment, this invention relates to animproved process of producing image dye in an imagewise-exposedphotographic element having a support and at least one layer thereoncontaining a silver halide emulsion having associated therewith an imagedye-providing color coupler wherein said process comprises 1)development of said imagewiseexposed photographic element with a silverhalide developing agent to produce an imagewise distribution of metallicsilver and imbibition of a color-developing agent in said photographicelement and then 2) contacting said photographic element which containssilver halide and said imagewise distribution of metallic silver with anamplifier composition which represses substantially additional netsilver development, wherein said amplifier composition contains acobalt(lll) metal complex having a coordination number of 6 and saidamplifier composition is maintained in contact with said photographicelement under conditions which reduce cobalt(lIl) to cobalt(ll), whichin turn oxidizes said color-developing agent whereby additional imagedye is provided from said image dye-providing color coupler and saidoxidized color-developing agent.

The elements processed, as above, can, of course, be bleached, fixed andwashed, etc., in the normal manner after contact with the amplifier.Generally, the improved processes of this invention reduce the necessityof fixing the silver halide out of a photographic element beforeamplification and also reduce the problems associated with silver halidedevelopment in an amplifier bath wherein the amount of catalytic silverformation may be very dependent on conditions, reaction byproducts, etc.Generally, this process also provides highly improved stability ofdevelopment compositions and amplifying compositions and is especiallysuited to continuous processing of color photographic elements. Theprocess is especially advantageous in processing multicolor photographicelements since stability in processing solutions is highly improvedallowing reproducible results over long periods of operating time.

In one preferred embodiment, the amplifier solution contains asufficient quantity of a development restrainer or combination ofdevelopment restrainers to repress substantially any further net silverdevelopment.

In another embodiment, the color-developing agent is an aromatic primaryamino compound and is preferably a phenylenediamine color-developingagent.

In another preferred embodiment where high rates of processing aredesired, the photographic element is developed in an aqueous bath andcontacted with an amplifying solution which is maintained attemperatures above 90 F. and preferably above 100 F. The process of thisinvention enables one to achieve low wet times in processing since thebaths are relatively stable at high temperatures.

In another preferred embodiment, the photographic element is developedin a liquid which is substantially free of a cobalt(lll) metal complexhaving a coordination number of 6. I

In another preferred embodiment, the amplifier solution is substantiallyfree of silver halide solvents or contains less than 30 percent, byweight, of the amount of silver halide solvent which would be necessaryto fix the silver halide emulsion in the element being processed.

In another embodiment, the photographic elements processed in accordancewith this invention preferably contain a water-insoluble imagedye-providing color coupler dissolved in a coupler solvent.

In still another embodiment, the photographic element is processed in abath containing a coupling accelerator which is an alcohol and theamplifier solution preferably contains a coupling accelerator which isan alcohol.

In a highly preferred embodiment, this invention relates to an improvedprocedure for processing a multicolor photographic element comprising atleast two color-providing layer units which each contains a silverhalide emulsion and an image dye-providing color coupler in at least a40 percent and preferably a 70 percent stoichiometric excess based oneffective silver coverage in said layer. When the photographic elementof this embodiment is a three-color element, the red and green recordinglayers are preferably in accordance with said color-providing layerunits above, and. the blue recording layer can be coated in accordancewith said definition, but where it is necessary to obtain differentialphotographic speed between the blue recording layer and other recordinglayers, it may be desirable to use high coverages of silver anddifferent ratios of coupler to silver in the blue-sensitive layer.

In still another highly preferred embodiment, the photographic elementsof this invention comprise at least one and preferably two imagedye-providing layer units wherein the silver halide is coated at acoverage of less than 30 mg. of silver per ft.

In a highly preferred embodiment, a development restrainer is used inthe amplifier bath in sufficient quantities to repress substantiallyfurther development of silver halide. Improved fog levels can beobtained if development is not allowed to proceed in the amplificationbath, especially in continuous processes where one may encounter ammoniabuildup in the amplifier.

In one embodiment, the preferred development restrainers arewater-soluble bromide compounds such as KBr, etc., or heterocycliccompounds such as tetrazoles, azaindines and triazoles which are free ofmercapto or ionic iodide groups. Development restrainers as a class ofcompounds are known in the art, as mentioned in US. Pat. No. 3,458,317issued July 19, 1969. Development restrainers which have ionic iodidegroups or mercapto groups appear to retard the catalytic effect ofsilver. Typical preferred development re strainers include high levelsof KBr such as 2 to 40 g./l., methyl benzotriazole, benzotriazole,3-methyl-l ,3- benzothiazolium bromide, S-nitrobenzimidazole,decamethylene bis(benzothiazolium bromide), and the like. Other usefulorganic development restrainers include the sodium salt of4-hydroxy-6-methyl-1,3,3a,7- tetrazaindene, the sodium salt of4-hydroxy-6-methyl- 2-methylmercapto-l ,3 ,3 a,7-tetrazaindene, 4,5-dihydro-l ,4-diphenyl-3,S-phenylamino-l ,2,4-triazole and the like. Theheterocyclic development restrainers are generally incorporated in theamplifier at concentrations of 0.01 to 2.0 g./l. In certain embodiments,the heterocyclic groups containing sulfur substitution can be used asdevelopment restrainers where the compound as used in the amplifierremains in its thione form rather than in the thiole or mercapto form.In highly preferred embodiments, a combination of an alkali metalbromide and an organic development restrainer are present in theamplifier composition.

The amplifying baths of this invention preferably contain only lowamounts or are substantialy free of silver halide solvents. If highamounts of solvents are present, there is very little noticeableamplification effeet in the bath. Therefore, the amplifying bathsgenerally comprise less than 30 percent by weight of the amount of asilver halide solvent which would be necessary to fix a silver halideemulsion. The fixing processes are well-known in the art, for example,as disclosed in Stephen, U.S. Pat. No. 3,615,508 issued Oct. 26, 1971.

As used herein, the terms photographic color coupler and imagedye-providing color coupler" include any compound which reacts (orcouples) with the oxidation products of primary aromatic aminodeveloping agent on photographic development to form an image dye, andare nondiffusible in a hydrophilic colloid binder (e.g., gelatin) usefulfo photographic silver halide, and also those couplers which provideuseful image dyes when reacted with oxidized primary aromatic aminodeveloping agents such as by a couplerrelease mechanism. The couplerscan form diffusible or nondiffusible dyes. Typical useful color couplersinclude phenolic S-pyrazolone and open-chain ketomethylene couplers.Specific cyan, magenta and yellow dye-forming couplers which can beemployed in the practice of this invention are described in Graham etal, U.S. Pat. No. 3,046,129 issued Jan. 24, 1962, column 15, line 45,through column 18, line 51, which disclosure is incorporated herein byreference. Such color couplers can be dispersed in any convenientmanner, such as by using the solvents and the techniques described byU.S. Pat. No. 2,322,027 by Jelley et al issued June 15,1943, or U.S.Pat. No. 2,801,171 by Fierke et al issued July 30, 1957. When couplersolvents are employed, the most useful weight ratios of color coupler tocoupler solvent range from about 1:3 to 120.1. The useful couplersinclude Fischer-type incorporated couplers such as those described inFischer, U.S. Pat. No. 1,055,155 issued Mar. 4, 1913, and particularlynondiffusible Fischer-type couplers containing branch carbon chains,e.g., those referred to in the references cited in Frohlich et al, U.S.Pat. No. 2,376,679 issued May 22, 1945, column 2, lines 50-60.Particularly useful in the practice of this invention are thenondiffusible color couplers which form nondiffusible dyes.

In certain preferred embodiments, the incorporated couplers in the layerunits of this invention are waterinsoluble color couplers which areincorporated in a coupler solvent which is preferably a moderately polarsolvent. Typical useful solvents include tri-o-cresyl phosphate,di-n-butyl phthalate, diethyl lauramide, 2,4- diarylphenol, liquid dyestabilizers as described in an article entitled Improved PhotographicDye Image Stabilizer-Solvent, Product Licensing Index, Vol. 83, March,1971, and the like. The coupler solvents in the elements appear to aidthe imbibition of color developer where it is carried into an amplifierbath via the element.

The photographicelements processed in accordance with this inventiongenerally comprise a light-sensitive silver halide emulsion wherein thehalide is generally less than 6 mole percent iodide and preferably lessthan 3 percent iodide and, in some highly preferred embodiments, is lessthan 0.25 percent iodide. If iodide is near the surface of the emulsiongrains, it can build up in the solutions at a high level duringdevelopment and amplification and affect dye production in theamplification step. Therefore, high amounts of iodide in the emulsionare generally avoided, especially when the element is to be processed ina continuous-process apparatus.

The term nondiffusible used herein as applied to couplers and productsderived from couplers has the meaning commonly applied to the term incolor photography and denotes materials which for all practical purposesdo not migrate or wander through photographic hydrophilic colloidlayers, such as gelatin, particularly during processing in aqueousalkaline solutions. The same meaning is attached to the term immobile."The terms diffusible and mobile have the converse meaning.

The photographic elements of this invention, as defined above, comprisea support having thereon image dye-providing layer units. A multicolorphotographic element comprises at least two of said image dyeprovidinglayer units which each records light primarily in different regions ofthe light spectrum. The layer unit comprises a light-sensitive silversalt, which is generally spectrally sensitized to a specific region ofthe light spectrum, and has associated therewith a photographic colorcoupler. In certain embodiments, the colorproviding layer units areeffectively isolated from other layer units by barrier layers, spacerlayers, layers containing scavengers for oxidized developer and the liketo prevent any substantial color contamination between the imagedye-providing layer units. The effective isolation of the layer units isknown in the art and is utilized to prevent color contamination in manycommercial color products.

The photographic elements of this invention preferably comprise asupport having thereon at least one image dye-providing layer units andpreferably at least two image dye-providing layer units containing alightsensitive silver salt, preferably silver halide, having associatedtherewith a stoichiometric excess of coupler of at least 40 percent andat least preferably percent. The equivalency of color couplers is knownin the art, for example, the 4 equivalent couplers require 4 moles ofoxidized color developer, which in turn requires development of 4 molesof silver, to produce 1 mole of dye. Thus, for a stoichiometric reactionwith silver halide one equivalent weight of this coupler will be 0.25mole. In accordance with this embodiment, the color image-providing unitcomprises at least a 40 percent excess of the equivalent weight of imagedye-providing color coupler required to react with the silver andpreferably a 70 percent excess of said coupler based on effectivesilver. In certain highly preferred embodiments, the photographic colorcouplers are employed in the image dye-providing layer units at aconcentration of at least three times, such as from three to 20 times,the weight of the silver in the silver halide emulsion, or at astoichiometric excess of at least 1 10 percent based on effective silverin said layer unit. Advantageously, the coupler is present in an amountsufficient to give a density of at least 1.7 and preferably at least 2.0when coated on a paper support and preferably at least 3.0 when coatedon a transparent film support. Generally, the coupler is present in saidlayer units in at least 1 X 10 moles/ftF. Preferably, the differencebetween the maximum density and the minimum density (which can compriseunbleached silver) is at least 0.6 and preferably at least 1.0.Preferably, the photographic elements prepared in accordance with thisinvention are those described in Bissonette, U.S. Ser. No. 256,072,entitled Photographic Elements, filed on even data herewith andincorporated herein by reference.

Advantageously, the photographic color couplers utilized are selected sothat they will give a good neutral. Preferably, the cyan dye formed hasits major absorption between about 600 and 700 nm., the magenta dye hasits major absorption between about 500 and 600 nm., and the yellow dyehas its major absorption between about 400 and 500 nm.

Generally, each of the color-providing layer units of the photographicelements contains a light-sensitive silver halide. In one preferredembodiment, the colorproviding layer units comprise a silver salt at aconcentration of up to 30 mg. of silver per square foot. However, whilethe silver halide is preferably present at concentrations based onsilver of less than 30 mg./ft. it is possible to coat emulsions athigher silver coverages within this embodiment, as long as no more than30 mg./ft. of silver develops; for example, such emulsions may containsilver halide grains which are relatively light-insensitive or maycontain developer restrainers such as development inhibitor-releasingcoupiers, and still provide a photographic element whichisadvantageously used in the various processes as described herein toproduce improved image records. In some instances, relativelylight-insensitive silver halide grains or development restrainers aredesirable to enable one to obtain more uniform coating coverage withless precise coating equipment, as well as for other reasons. Thus,highly preferred photographic elements processed according to thisinvention contain at least two color-providing layer units, eachcontaining a silver halide emulsion, defined in terms of effectivecoverage and developability, as one which, when it is fully exposed andprocessed for about 1 minute at 100 F. in Developer A as described inExample 1, will provide less than 30 mg. of metallic silver per ft. andpreferably less than 15 mg./ft. It is understood that the term effectivesilver refers to that amount of silver which is produced in this testand that ratios of coupler to silver are based on effective silver whichis produced by this type of development when so specified herein. Inmost instances, the quantity of effective silver as silver halide in theundeveloped, unexposed photographic element will be quite similar toquantity of total silver present as silver halide. The fully exposedlayer containing silver halide emulsion is one which is exposed to Dmaxas is well-known in the art, for example, by exposue exposure aSOD-watt, 3000K lamp for about seconds (total exposure at the film plane113 X 10 ergs./cm.

The photographic elements processed in accordance with this inventiongenerally can contain negative silver halide emulsions, direct-positivesilver halide emulsions, silver halide emulsions designed for processingin reversal processes, and the like. It is understood, of course, thatwith negative emulsions the catalytic metallic silver development willbe in the exposed areas whereas with direct-positive emulsions thecatalytic metalic silver will be formed in the unexposed areas.

The amplifiers of this invention comprise a cobalt (1!!) metal complex.Such complexes feature a molecule having a cobalt atom or ion. Thiscobalt atom or ion is surrounded by groups of atoms, ions or othermolecules which are, generically referred to as ligands. The cobalt atomor ion in the center of these complexes is a Lewis. acid; the ligandsare Lewis bases. Werner complexes are well-known examples of suchcomplexes. The useful cobalt salts are typically capable of existing inat least two valent states. In a preferred aspect of the invention, thecobalt complexes are those referred to by American chemists as inert andby European chemists as robust. Particularly useful are complexes of acobalt ion with a ligand which, when a test sample thereof is dissolvedat 0.1 molar concentration at 20 C. in an inert solvent solution alsocontaining 0.1 molar concentration of a tagged ligand of the samespecies which is uncoordinated, exhibits essentially no exchange ofuncoordinated and coordinated ligands for at least 1 minute, andpreferably for at least several hours, such as up to 5 hours or more.This test is advantageously conducted under the pH conditions which willbe utilized in the practice of the invention. In silver halidephotography, this generally will be a pH of over about 8. Many cobaltmetal complexes useful in this invention show essentially no exchange ofuncoordinated and coordinated ligands for several days. The definitionof inert metal complexes and the method of measuring ligand exchangeusing radioactive isotopes to tag ligands are well-known in the art;see, for example, Taube, Chem. Rev., Vol. 50, p. 69 (1952) and Basoloand Pearson, Mechanisms of Inorganic Reactions, A Study of MetalComplexes and Solutions, 2nd Edition, 1967, published by John Wiley andSons, p. 141. Further details on measurement of ligand exchange appearin articles by Adamson et al, J. Am. Chem. Soc., Vol. 73, p. 4789(1951). The inert metal complexes should be contrasted with labilecomplexes which, when tested by the method described above, have areaction half-life generally less than 1 minute. Metal chelates are aspecial type of metal complex in which the same ligand (or molecule) isattached to the central metal ion at two or more different points. Themetal chelates generally exhibit somewhat slower ligand exchange thannonchelated complexes. Labiletype chelates may have a half-life ofseveral seconds, or perhaps slightly longer. Generally, the oxidizingagents employed are not reduced to a zero valent metal during the redoxreaction of the invention. 7

Preferred cobalt complexes in accordance with this process havecoordination numbers of 6 and are known as octahedral complexes. Cobaltcomplexes are especially useful in the practice of this invention.

A wide variety of ligands can be used with a metal ion to form suitablecobalt complexes. Nearly all Lewis bases (i.e., substances having anunshared pair of electrons) can be ligands in cobalt complexes. Sometypical useful ligands include the halides, e.g., chloride, bromide,fluoride, nitrite, water, amino, etc., as well as such common ligands asthose referred to on page 44 of Basolo et al, supra. The lability of acomplex is influenced by the nature of the ligands selected in formingsaid complex.

Particularly useful cobalt complexes have a coordination number of 6 andhave a ligand selected from the group consisting of ethylenediamine(en),propylenediamine(tn), diethylenetriamine(dien),triethylenetetraamine(trien), ammine(Nl-I 'nitrate, nitrite, azide,chloride, thiocyanate, isothiocyanate, water and carbonate. Thepreferred cobalt complexes comprisel) at least two ethylenediamineligands or 2) at least five amine ligands or 3) onetriethylenetetraamine ligand. Especially useful are the cobalt hexarnmine salts (e.g., the chloride, bromide, sulfite, sulfate, perchlorate,nitrite and acetate salts). Some other specific highly useful cobaltcomplexes include those hav ing one of the following formulas: rco 1vu,,n,o1x; [CO(NH:;)5CO3]X; 3)s l a)' CO ]X; [Co(en) 1X; cis-[Co(en) (N ]X;trans- [Co(en) Cl(NCS)]X; trans-[Co(en) (N ]X; cis- [Co(en) (NH )N ]X;cis-[Co(en) Cl ]X'; transl )2 2l )2( )2] )2( )z] )al l )2( and[Co(tn)(en) ]X; wherein X represents one or more anions determined bythe charge neutralization rule.

With many complexes, such as cobalt hexammine, the anions selected cansubstantially effect the reducibility of the complex. The following ionsare listed in the order of those which give increasing stability tocobalt hexammine complexes: bromide, chloride, nitrite, perchlorate,acetate, carbonate, sulfite and sulfate. Other ions will also effect thereducibility of the complex. These ions should, therefore, be chosen toprovide complexes exhibiting the desired degree of reducibility. Someother useful anions include chloride, nitrate, thiocyanate, dithionateand hydroxide. Neutral complexes such as [Co(dien)(SCN) OH] are useful,but positively charged complexes are generally preferred.

A theory has been advanced to explain the low reactivity between thereducing agent and the central metal atom or ion of the metal complex.It appears that the ligands constitute an effective barrier to reactionbetween reducing agents and the central metal atom or ion. The barriermay be set up by ligands tightly bound to and surrounding the centralmetal atom or ion. In the presence of certain catalysts, it seems thatone or more of the ligands may be bound less tightly to the centralmetal atom or ion, thus facilitating reaction between the central metalatom or ion and the reducing agent. However, this invention is notlimited to that theory.

Numerous color-developing agents can be imbibed in the photographicelement in accordance with the present invention. The color-developingagents utilized herein undergo redox reaction with the oxidizing agentat a catalytic surface. Especially preferred colordeveloping agents arethose which reduce silver halide to metallic silver, such as those whichare capable of developing imagewise-exposed light-sensitive photographicsilver halide. Typical preferred colordeveloping agents are aromaticprimary amine colordeveloping agents such as p-aminophenols (which formparticularly stable redox combinations with certain complexes, e.g.,[Co(en) ]Cl or pphenylenediamines. Useful color-developing agentsinclude 3-acetamido-4-amino-N,N-diethylaniline, P-amino-N-ethyl-N-B-hydroxyethylaniline sulfate, N,N-diethyl-p-phenylenediamine, 2-amino-5- diethylaminotoluene, N-ethyl-N-B-methanesulfonamidoethyl-3-methyl-4-aminoaniline,4-amino-N-ethyl-3-methy1-N-([3-sulfoethyl)aniline, 4-amino-N-butyl-N-y-sulfobutylaniline, 4-amino-N,N-diethyl-3-n-propylaniline hydrochloride, and the like. See Bent et al,JACS, Vol. 73, pp. 3100-3125 (1951), and Mees and James, The Theory ofthe Photographic Process, 3rd Edition, 1966, published by MacMillan Co.,New York, pp; 27 8-31 1, for further typical, useful developing agents.It will be appreciated that many of the subject color-developing agentsare most effective at high pH, such as a pH from about 8 to 13.

In one highly preferred embodiment, aromatic primary aminocolor-developing agents which provide good results in the process ofthis invention are 4-amino-N,N-diethylaniline hydrochloride, 4-amino-3-methyl-N,N-diethylaniline hydrochloride, 4-amino-3-methyl-N-ethyl-N-B-(methanesulfonamido)ethylaniline sulfate hydrate,4-amino-3-methyl-N-ethyl-N-B- hydroxyethylaniline sulfate,4-amino-3-dimethylamino- N,N-diethylaniline sulfate hydrate, 4-amino-3-methoxy-N-ethyl-N-B-hydroxyethylaniline hydrochloride,4-amino-N-'ethyl-N-(2-methoxyethyl)-m-toluidine di-paratoluenesulfonate, and 4-amino-3-B- (methanesulfonamido)ethyl-N,N-diethylanilinedihydrochloride.

The black-and-white silver halide developers, as referred to herein,generally refer to those developers which do not couple withphotographic color couplers to form useful image dyes. Theblack-and-white silver halide developers can be effectively used in someinstances in the formation or development of the metallic silver in thephotographic element. Typical useful developers of this type includehydroquinones, catechols, 3-pyrazolidones such asl-phenyl-3-pyrazolidone, lphenyl-4,4-dimethyl-3-pyrazolidone,l-phenyl-4-methyl-3-pyrazolidone and the like, 1-, d or isoascorbicacid, reductones, N-methyl-p-aminophenols, and the like.

The amplifier bath can generally comprise any liquid as a carriermedium, but the liquid is preferably predominantly water. The bathgenerally comprises from about 0.2 to about 20 g. per liter of thetransition metal ion complex which preferably is maintained at betweenabout 1 to about 15 g./l. However, generally higher concentrations ofcobalt complexes can be used in preferred amplifier baths of thisinvention without adverse sensitometric effects compared withcolor-developing solutions which contain the cobalt complexes whichcontain sufficient color-developing agent to develop substantial amountsof silver halide rapidly.

The amplifier bath generally contains a development restrainer andpreferably contains enough development restrainer to repress any furthersilver formation. Thus, the sensitometric changes associated with thedevelopment of silver are avoided. Moreover, this feature enables one touse various grain sizes in various layers of a multicolor element toobtain a balanced photographic element and simultaneously providesubstantially uniform color formation in each layerywhereby balancedcolor can be obtained at several densities by inspection.

The organic development'restrainers (i.e., other than the inorganicdevelopment restrainers such as the alkali metal bromides) mentionedpreviously can be used in the bath in combination with the inorganicdevelopment restrainers or alone, but are preferably used in combinationwith alkali metal bromides. Generally, the organic developmentrestrainers are used in concentrations of from 0 to 2 g. and preferablyfrom 0.01 to l g./l.

The amplifier bath is generally operated in a pH range of from 6 to '14and preferably at pH ranges of 8 to 12.

The amplifying baths contain only small amounts of or are substantiallyfree of silver halide solvents such as sodium thiosulfate, thiocyanates,thioethers and the like. While bromide ions are often desirable in smallamounts of about 2 to 40 g./l. of amplifying solution to repressdevelopment, high concentrations such as above 200 g./l. could functionto bleach silver halide layers and, likewise, defeat the primaryamplification step. In certain embodiments, it is also desirable tomaintain the ammonia in the amplifier at less than 10 g./l. since highammonia concentrations can act as a silver halide solvent, thus allowingbleaching of the silver image.

The term silver halide solvents generally refers to compounds andconcentration levels of those compounds which, when employed in anaqueous solution C.), are capable of dissolving more than ten times theamount (by weight) of silver chloride than that which can be dissolvedby water at 60 C.

The concentration of a solvent necessary to fix a silver halide layer isunderstood to mean that concentration of solvent in a liquid bath whichwill remove substantially all silver bromide from a photographic elementcontaining a single silver bromide gelatin emulsion layer coated at 30mg. silver per ft. in 1% minutes at 105 F. maintained at a pH rangewithin 4.0l2.0.

The amplifier bath is generally maintained under conditions to repressfurther net metallic silver formation in the photographic element.However, since color developer can be carried into the amplifier bath incertain embodiments by imbibition in the element, buildup of colordeveloper in the bath can occur. Generally, in those embodiments theconcentration of color developer in the amplifier solution is maintainedbelow 3 g./l. and preferably below 1 g./l. of amplifier solution. Withthe higher concentrations of color developer, such as above 0.5 g./l.,it is desirable to incorporate an antioxidant in the amplifier bath,such as sulfites and the like. In certain embodiments where exactsensitometric effects are desired throughout the run, the concentrationof the color developer is maintained at a constant level. In certainpreferred embodiments, color-developer scavengers and the like are usedin the bath to keep the amplifier bath substantially free of unoxidizedeffective color developer.

Generally, with most color developers sufficient unoxidized colordeveloper can be imbibed in the photographic element so that developerexhaustion is not a severe problem in amplification of the dye image.However, the changes in the concentration of the color developer in theamplifier can vary the time required in the amplifier bath since thecolor developer apparently diffuses out of the element more rapidly whenthe color-developing agent concentration in the amplifier bath is verylow. However, the problem of variations in color-developer concentrationis minimal when continuous processes are used, such as continuous webprocesses.

In one embodiment, the highly preferred organic development restrainerswhich are useful in the amplifiers of this invention can be furthercharacterized by the following test. Preferred organic developmentrestrainers or combinations of development restrainers with an alkalimetal bromide are those which, when incorporated at about 200 mg./l. ina bath of the following composition:

toluidene di-p-toiuene sulfonate water to l liter pH [0.1 at 75 F.

will produce a substantially equal or higher Dmax and a substantiallyequal or lower Dmin than a similar sample processed in the bath withoutthe development restrainer wherein the sample is a photographic elementcomprising a transparent support and one emulsion layer thereoncomprising a silver chlorobromide emulsion at 30 mg. of Ag/ft. andsufficient color coupler to produce a Dmax of at least 3.0 when reactedon an equal stoichiometric basis with oxidized color developer, such asoxidized 4-amino-N-ethyl-N-(2- methoxyethyl)-m-toluidine-di-paratoluenesulfonate, and said element is first fully exposed to Dmax and developedin a black-and-white developer such as Kodak Developer D-l9 for 4minutes at room temperature and fixed with sodium thiosulfate to removesubstantially all undeveloped silver halide.

Several of the organic development restrainers have an additive orsuperadditiVe effect when used in combination with an alkali metalbromide as shown in some of the following examples.

The amplifier bath can be operated over a wide range of temperaturesdepending on the effect desired. Generally, the amplifier bath is muchmore stable than amplifier baths previously used and, therefore, ispreferably used in processes where it is operated at temperatures aboveF. and more preferably above F. to decrease the residence time of aphotographic element in the bath, thus speeding up the process. Theamplifier baths of this invention which are held for l week at F.provide substantially the same development properties as a freshamplifier bath.

The developing baths and amplifier solutions of this inventionpreferably contain a coupling accelerator which can be an alcoholincluding aromatic alcohols such as benzyl alcohol, which appears toincrease dye yields. Preferably the alcohol is used in the respectivebaths at a concentration of up to 40 g.ll. and preferably from about 2g. to 20 g./l. Coupling accelerators are known in the art, for example,the alcohols disclosed in U.S. Pat. No. 2,304,925 by Jelley issued Dec.15, 1942, U.S. Pat. No. 2,950,920 by Schwan et al issued Aug. 30, 1960,and the like.

The improved processes of this invention can be carried out in severaltypes of processing equipment. Simple manual tray or dip tank processingcan be used, as well as processes as described by Tregillus et al, U.S.Pat. No. 3,179,517 issued Apr. 20, 1965, roller transport processes asdescribed in Russell et al, U.S. Pat. No. 3,025,779 issued Mar. 20,1962, and the like. Preferably, the process is carried out in aunidirectional processing equipment where the element leaves a bath inthe same relative direction with respect to the plane of the element asit enters the bath. In certain preferred embodiments, a continuous webof the photographic material is processed in unidirectionalcontinuousprocessing equipment.

In still other embodiments, the processing solutions can be used inimage transfer processes with the developer and amplifier put inseparate rupturable pods, such as in the general format as disclosed inCole, U.S. Pat. No. 3,635,707 issued Jan. 18, 1972, and the like.

Several features of the present process are apparent from FIGS. 1-4accompanying this application.

FIG. 1 is an H and D curve of the image records of Example 1.

FIG. 2 is an H and D curve of the image records of Example 3, with thecurves for the respective imagerecording layers separated for claritywith the caret indicating the point of the 1 1th step on the2l-stepwedge sensitometric exposure for each set of curves.

FIG. 3 is an H and D curve of the image records of Example 4.

FIG. 4 is an H and D curve of the image records of Example 6. Thedesignations B, G and R refer to the curves produced by theblue-sensitive layer unit, the green-sensitive layer unit and thered-sensitive layer unit respectively.

The invention can be further illustrated by the following examples.

The improvements in amplifying the image record in the red and greenrecording layer of a photographic element are readily apparent whenprocessing by first developing the element in a color developer and theninserting the element containing silver halide and an imagewisedistribution of metallic silver into an amplifier bath.

A photographic element is prepared by coating the following layers inorder on a paper support:

1. a layer containing a blue-sensitive AgClBr emulsion at 16 mg. Ag/ftF,gelatin at 150 mg./ft. and a 2-equivalent coupler, yellow dye-formingcoupler a-pivalyl-a-[4-(4-benzyloxyphenylsulfonyl)phenoxy]-2-chloro-5-['y-(2,4-di-tert-amylphenoxy)butyramido]acetanilide, at 75 mg./ft. dissolvedin di-n-butyl phthalate coupler solvent at 18.75 mg./ft.";

2. a gelatin interlayer at 80 mg./ft.

3. a layer containing a green-sensitive AgClBr emulsion at mg. of Ag/ft.gelatin at 60 mg./ft. and a 4-equivalent magenta coupler, magentadyeforming coupler l-(2,4,6-trichlorophenyl)-3-{5-[a-(3-tert-butyl-4-hydroxyphenoxy)tetradecaneamidol2-chloroanilino}-5-pyrazolone, at 25 mg./ft. dissolved in tri-cresylphosphate coupler solvent at 12.5 mg./ft.

4. a gelatin interlayer containing 231 mg. gelatin/f0;

5. a layer containing a red-sensitive AgClBr layer at 6 mg. Ag./ft.gelatin at 65 mg./ft. and a 2- equivalent cyan coupler, cyan dye-formingcoupler 2-[a-(2,4-ditert-amylphenoxy)butyramido]-4,6-dichloro-S-methylphenol, at 35 mg./ft. dissolved in di-n-butyl phthalatecoupler solvent at 17.5 mg.- /ft.

6. a gelatin overlayer at 80 mg./ft. of gelatin.

Samples of the coating are sensitometrically exposed to agraduated-density test object and then processed at a temperature of 32C. in the following sequence:

Test 1A (Control) Test 18 color-develop 3.5 min. 3.5 min. amplify l min.bleach-fix 1.5 min. 1.5 min. wash 2 min. 1 min. stabilize l min. 1 min.

The respective baths have the following compositions:

Color Developer A water to 1 liter 114 pH6.8 at F.

Stabilizer citric acid 6.15 g acetic acid 13.1 g benzoic acid 0.34 g KOH5 97 g water to 1 liter pH 3.60 at 80 F.

Test 1A is run at the optimum time of development to produce Dmax withthe cyan and magenta dyes. While this amount of developed silver is morethan necessary for the amplification process of Test 13, the developmenttime is held constant to show that the amplification step will generateadditional dye beyond that provided in the development step.

The H and D curves of the elements of Tests 1A and 1B are produced inFIG. 1. The density of the dyes produced in the red-, blueandgreen-sensitive layers are reported as dashed lines for Test 1A andsolid lines for Test 18.

In the above process, sufficient color developer is carried into theamplifier bath to produce the desired dye density. If additional densityis desired, more color developer can be added to the amplifier bath orlonger times can be used in the amplifier bath. The KBr in the aboveamplifier appears to suppress development sufficiently to allow theamplification step to be carried out in roomlight.

EXAMPLE 2 EXAMPLE 3 Additional samples prepared and exposed as describedin Example 1 are processed by the procedure of Test 1B, except thedevelopment time is 15 seconds and the amplification step is run at 1, 2and 3 minutes in separate tests.

Separated H and D curves for each layer matched at common thresholdspeeds are shown in FIG. 2. The results indicate that a dye image can beattained with a limited quantity of initially developed catalytic imagesilver if the dwell time of the photographic material in the amplifierbath is prolonged. It is also observed in a separate processing run thatthe combination 2minute color development/S-minute amplification doesnot lead to a higher density of image dye than a combination l-minutecolor development/3-minute amplifica-, tion. However, speed and fogincrease with prolonged development time.

It is observed that by controlling the time in the amplifier bath, colorimages of variable contrast and constant threshold speed can now beproduced with one and the same reflection print material. Such contrastcontrol is attainable in conventional photographic processes only withgreat difficulty. This aspect of my invention is in part illustrated inFIG. 2. However, in order to obtain better color balance with thephotographic element, it is apparent that longer initial developmenttimes are desirable to obtain more silver in the blue-sensitive layer.This longer development time is demonstrated in the following example.

EXAMPLE 4 The imagewise-exposed element of Example 1 is processedaccording to procedures below to provide for better developability ofthe blue-sensitive layer:

Minutes at 100 F.

Test 4A Test 4B develop 1 1 amplify O 3 bleach-fix 1% 1% wash 2 2stabilize 1 1 The developer, bleach-fix and stabilization baths are thesame as Example 1, and the amplification bath is made as follows:

Water to 1 liter pH 10.1 at 75 F.

The results are shown in FIG. 3 on an H and D curve where the solidlines represent Test 48 and the dashed lines represent the results ofTest 4A. The bluesensitive layer apparently produces more catalyticsilver than is shown in Example 3, and as a result provides improvedmatched dye production in the amplification bath. This amplifier isdesigned to give high contrast and low sensitivity to build-up effects.This includes carry-over of the color developing solution and subsequentbuildup of ammonia in the amplifier. Similar results are obtained withthe concentrations of 5- methylbenzotriazole of about 0.3 g./l. The 5-methylbenzotriazole prevents development and fog growth, thusstabilizing the overall process response.

EXAMPLE 5 A repeat of the procedures of Test 48 of Example 4 is madewherein the [Co(NH ]C1 is replaced with equimolar amounts respectivelyof [Co(Nl-I H O]Cl )2( )lz' 3)5( 2 4)3,

With each of the cobalt metal complexes a useful dye image is obtained.

EXAMPLE 6 A photographic element is prepared and imagewiseexposed asdescribed in Example 1 and processed as follows:

Test 6A Test 68 Test 6C at 105 F. at 105 F. at 120 F. develop 1 min. 1min. sec. amplify 2 min. 0 min. 45 sec. bleach-fix 1 min. 1 min. sec.wash 1% min. 1% min. 45 sec. Total: 5% min. 2 min., 25 sec. Thedeveloper is as follows:

benzyl alcohol 15 ml.ll. K,CO, 30 g./l.

KBr 0.5 gJl. M80, 4.0 gJl. hydroxylamine sulfate 2 gJl.4-amino-N-ethyl-N-(Z-methoxyethyU-m- 7.5 g./l. toluidine di-paratoluenesulfonate diarnino propanol tetraacetic acid 3.0 g./l. Water to 1 literpH 10.08 at F.

The amplifier has the following composition:

benzyl alcohol 15 mL/l. K 2 g./l. KBr 5 g./l. [Co(Nl-l ]Cl 1O g./l. K CO7.5 gJl. diamino propanol tetraacetic acid 10 g./1.S-methylbenzotriazole 0.3 g.ll. Water to 1 liter pH 10.1 at 75 F.

The bleach-fix bath is as follows:

ammonium thiosulfate 60% 150 ml. Na SO 15 g./l. diamino propanoltetraacetic acid 3 gjl. glacial acetic acid 20 ml./l. [Co(NH;,) ]C1;, 3g./l.

water to 1 liter pH 4.5 at 75 F.

The element processed in Test 6A at 105 F. produces a good image recordwith a sensitometric H and D curve as shown in FIG. 4. The H and D curvewhere no amplification is used is shown in FIG. 4 in dashed lines. It isapparent that good matched color production can be obtained bycontinuing to amplify the catalytic silver in each respective layer.Thus, one can raise the contrast and dye Dmax by controlling developmentand amplification.

The developing solution and amplifier solution are held at 105 F. forextended periods of time with periodic processing of similar elements.After 7 days there are no significant changes apparent in the recordsproduced in this system.

In the above amplifying bath a combination of an inorganic developmentrestrainer, KBr and an organic development restrainer,S-methylbenzotriazole, are used to repress additional development andfog. Comparing FIGS. 3 and 4, it is apparent that the fog levels arereduced by the combination of the development restrainers.

The elements processed in Test 6C produce a sensitometric curve verysimilar to Test 6A, but the total processing time is considerablyreduced.

In this example, the bleach-fix bath is preferably maintained with acobalt metal salt level of about 2 to 6 g./1. This can be achieved byaddition or carry-over from the amplifier bath.- When 10 g./1. arepresentin the amplifier bath, enough cobalt salt is apprently apparentlyinto the bleach-fix solution to keep the level at about 3 g./1 with mostmulticolor photographic elements.

EXAMPLE '7 Test 6A is repeated with the photographic element which isprepared and imagewise-exposed as described in Example 1, with theexception that the amplifier bath is used for only 1% minutes and the[Co(NH;,) ]Cl is replaced, respectively, with equimolar amounts of[Co(NH ](C l-1 O [Co(NH 03 [CO(NHS)B]Z(SO4)3! a)s( 2 a 2)]( a)2 and a)52 C Good dye images are obtained in each instance which have much higherdensity than the control run through Test 68.

EXAMPLE 8 EXAMPLE 9 A photographic element prepared and imagewiseexposedas described in Example 1 is processed in a continuous process asfollows:

developer 1 min. amplifier 1% min. bleach-fix 1 min. wash 1% min.

The amplifier, bleach-fix and wash are the same as in Example 6. Thedeveloper is varied in each test to the constituency as follows:

Test A Test B Test C Test D benzyl alcohol 15 g./l. same same same loco,3O g./l. same same same KBr 0.5 g./l. same same same hydroxylamine sul-2.0 g./l. same same same fate diamino propanol 3.0 g./l. same same sametetraacetic acid 4-amino-N-ethyl-N- 2.5 gJl. 7.5 g./l. 5.0 g./l. 2.5gJl. (2-methoxyethyl)- m-toluidine di-ptoluene sulfonate1-phenyl-4,4-di- 0 25 mgJl. 100

mg./l.

methyl-3-pyrazolidone Water to 1 liter The element developed in Test Awith low amounts of color developer produces low yellow dye density buta cyan density of 2.3 and a magenta density of about 1.9. Tests B, C andD all produce dye densities in the element of yellow, cyan and magentaof about 2.0-2.4. Thus, as more black-and-white developer is added tothe developing solution, the concentration of the colordeveloping agentcan be reduced and high dye densities can still be achieved in theamplification bath.

The use of lower concentrations of color developer in the developer bathaids in preventing buildup of the color-developing agent inthe amplifierbath, thus alleviating problems associated with any buildup of colordeveloper.

EXAMPLE A photographic film element is prepared as follows (with allingredients as listed in mg./ft.

1. cellulose acetate support;

2. a layer containing a blue-sensitive silver bromoiodide emulsion(1.14% iodide) at 61 mg. of Ag (1.0 micron grain), the yellow couplera-pivalyl-a-(4-carboxyphenoxy)-2-chloro-5-['y-(2,4-di-tert-amylphenoxy)butyramido1acetanilideat 132 mg. disolved 1:1 in tricresyl phosphate, and gelatin at 253 mg.;

3. layer containing gelatin at 43 mg.;

4. layer containing a red-sensitive silver chlorobromide (/20) emulsion(0.25 micron grain size) at 10 mg. of silver, a cyan coupler2-[a-(2,4-di-tertamylphenoxy)butyramido]-4,6-dichloro-5- methylphenol at79 mg. dissolved 1:3 in di-n-butyl phthalate, and gelatin at 207 mg.;

5. layer containing gelatin at 43 mg.

6. layer containing green-sensitive silver chlorobromide (80/20)emulsion (0.25 micron grain size) at 20 mg., magenta coupler1(2,4-dimethyl-6- chlorophenyl-Zl-]a-(3-n-pentadecylphenoxy)-butyramido1-5-pyrazolone at 139 mg. dissolved 1:1 in di-n-butylphthalate, and gelatin at 162 mg.;

7. layer containing gelatin at 68 mg.

Samples of the film element are exposed on a sensitometer and processedas follows:

Test 10A F.) Test 1013 (105 F.)

water to 1 liter pH 10.65 at 75 F.

The bleach-fix bath is as described in Example 6.

The densities for the samples processed in Tests 10A and 10B are asfollows:

Test 10A (control) Test 10B Dmin Dmax Dmin Dmax yellow 0.15 1.7 0.15above 3.7 cyan 0.15 1.46 0.15 above 3.2 magenta 0.15 1.64 0.15 above 3.7

It is apparent that photographic film elements having low silvercoverages can be processed to provide good image records where cyan,yellow and magenta dyes have high densities in the Dmax areas.

Although the invention has been described in considerable detail withparticular reference to certain preferred embodiments thereof,variations and modifications can be effected within the spirit and scopeof the invention.

I claim:

1. A process of providing or intensifying a visible image record in animagewise-exposed photographic element which comprises at least onecolor-providing layer unit which contains silver halide and an imagewisedistribution of metallic silver having associated therewith an imagedye-providing photographic color coupler, said process comprisingcontacting said photographic element in the presence of acolor-developing agent with an amplifier composition which contains 1) adevelopment restrainer in a concentration sufficient to represssubstantially additional net silver development and 2) a cobalt (ill)complex having a coordination number of 6, wherein said contact ismaintained under conditions which reduce cobalt (III) to cobalt- (II)and in turn oxidize said color-developing agent whereby image dye isformed from the color coupler in said layer unit and the oxidizedcolor-developing agent in the areas corresponding to the imagewisedistribution of metallic silver.

2. A process according to claim 1 wherein said colordeveloping agent isan aromatic primary amino compound.

3. A process according to claim 1 wherein said color- 'developing agentis imbibed in said photographic element before contact with saidamplifier composition.

4. A process according to claim 1 wherein said development restrainer isa benzotriazole compound.

5. A process according to claim 1 wherein said photographic element isdeveloped in an aqueous developer bath comprising a silver halidedeveloping agent before contact with said amplifier composition.

6. A process according to claim 5 wherein said silver halide developingagent is a primary aromatic amino compound.

7. A process according to claim 5 wherein said developer contains atleast two silver halide developing agents which comprise a primaryaromatic amino compound and at least one other compound which is ablack-and-white silver halide developing agent.

8. A process according to claim 5 wherein said silver halide developingagent is a black-and-white silver halide developing agent.

9. A process according to claim 1 wherein said photographic elementcomprises at least two of said colorproviding layer units.

10. A process according to claim 9 wherein each of said color-providinglayer units comprises said color coupler in at least a 40 percentstoichiometric excess based on effective silver.

11. in a process of developing an imagewise-exposed photographic elementcomprising a support and at least one image dye-providing layer unitthereon which contains a light-sensitive silver halide emulsion havingassociated therewith a color coupler, the improvement comprisingdevelopment of the imagewise-exposed silver halide emulsion to providean imagewise distribution of metallic silver and imbibition of acolordeveloping agent in said photographic element, and then contactingsaid photographic element with an amplifier composition which contains adevelopment restrainer in a concentration sufficient to represssubstantially additional net silver development and wherein saidamplifier solution contains a cobalt(lll) metal complex having acoordination number of 6 and said amplifier solution is maintained incontact with said photographic element under conditions which reducesaid cobaltflll) to cobalt(II) and in turn oxidize said color-developingagent to provide an increase in dye density with dye produced from saidcoupler in the areas corresponding to the imagewise distribution of saidmetallic silver.

12. A process according to claim 11 wherein said amplifier bath containsa sufficient quantity of development restrainer to repress substantiallyany further net silver development.

13. A process according to claim 11 wherein said color-developing agentimbibed in said photographic element is an aromatic primary aminocompound.

14. A process according to claim ll wherein said development of theimagewise-exposed silver halide emulsion is carried out in a liquidwhich is substantially free of cobalt (Ill) metal complex salts.

15. A process according to claim 11 wherein said amplifier bath issubstantially free of silver halide solvents or contains less than 30percent by weight of the silver halide solvent which would be necessaryto fix a silver halide emulsion.

16. A process according to claim 11 wherein the photographic element isdeveloped in solution and contacted with an amplifying bath which ismaintained at temperatures of above F.

17. A process according to claim 11 wherein said color-providing layerunit in said photographic element contains a silver halide emulsion inconcentrations of up to 30 mg. of silver per square foot.

18. A process according to claim 11 wherein said photographic element isa multicolor photographic element comprising at least twocolor-providing layer units which each contains a silver halide emulsionhaving associated therewith a photographic color coupler in at least a40 percent stoichiometric excess based on silver.

19. A process according to claim 11 wherein said photographic element isa photographic element comprising at least one image dye-providing layerunit which contains a silver halide emulsion having associated therewitha water-insoluble image dye-providing coupler dissolved in a couplersolvent wherein said coupler is present in at least a 40 percentstoichiometric excess based on effective silver.

20. A process according to claim 18 wherein each of said color-providinglayer units contains a silver halide emulsion at a concentration of lessthan 30 mg. of silver per square foot. 7

21. A process according to claim 11 wherein the halide concentration ofall silver halide emulsions in said element is less than 3 mole persentiodide.

22. A process according to claim 12 wherein said development restraineris substantially free of ionic iodide groups and free mercapto groups. p

23. A process according to claim 12 wherein said development restraineris the combination of from 0.0l to 2 g./l. of a benzotriazole and from 2g. to 40 g./l. of an alkali metal bromide.

24. A process according to claim 1 1 wherein said amplifier bathcontains from 2 g. to 40 g. of an alkali metal bromide.

25. A process according to claim 11 wherein said cobalt(Ill) metalcomplex is a cobalt hexammine salt.

26. A process according to claim 11 wherein said color-developing agentis 4-amino-N-ethyl-N-( 2- methoxyethyl)-m-toluidine di-p-toluenesulfonate.

27. A process according to claim 11 wherein said amplifier bath containsa coupling accelerator which is an alcohol.

28. A process according to claim 11 where.development of said silverhalide emulsion is carried out in a bath which contains a couplingaccelerator which is an alcohol.

29. A process according to claim 11 wherein the halide of the silverhalide emulsion in said element is less than 0.25 mole percent iodide.

30. A process according to claim 11 wherein said imagewise-exposedsilver halide emulsion is developed in the presence of a black-and-whitedeveloping agent.

31. A process according to claim 11 wherein said imagewise-exposedsilver halide emulsion is developed in the presence of an aromaticprimary amino compound and at least one other compound which is ablack-andwhite silver halide developing agent.

32. A process for developing an imagewise-exposed photographic elementcomprising a support having at least one layer unit thereon whichcontains a silver halide emulsion which has associated therewith atleast a 40 percent stoichiometric excess of an image dyeforming colorcoupler based on silver, which process comprises 1) a development stepwherein said photographic element is developed to form an imagewisedistribution of silver and an aromatic primary amino color-developingagent is imbibed in said photographic element, and then 2) contactingsaid photographic element with an amplifier bath containing a) a cobalt(III) metal complex having a coordination number of 6 and b) adevelopment restrainer for sufficient time to produce image dye inaddition to any dye produced in said development step.

33. A process for providing or intensifying an image record in animagewise-exposed photographic element comprising a support havingthereon at least one image dye-providing layer unit which contains alightsensitive silver halide emulsion and a dye imageproviding couplerin at least a 40 percent excess based on effective silver, comprisingthe steps of 1) developing said photographic element in the presence ofan aromatic primary amino color-developing agent and 2) contacting saidelement with an amplifier composition which comprises a cobalt(III)metal complex, an alkali metal bromide at a concentration of from 2 g.to 40 g./l., an organic development restrainer at a concentration offrom 0.01 to 2 g./l., and wherein said amplifier composition containsless than 30 percent by weight of the silver halide solvent which wouldbe necessary to fix said silver halide emulsion.

34. A process according to claim 33 wherein the temperature of theamplifier composition is maintained at above F.

35. A process according to claim 33 wherein said cobalt(IlI) metalcomplex is cobalt hexammine.

36. A process according to claim 33 wherein said image dye-providinglayer unit contains said color coupler in at least a percentstoichiometric excess based on effective silver.

37. A process for providing or intensifying an image record in animagewise-exposed photographic element comprising a support havingthereon at least two image dye-providing layer units each of whichcontains a light-sensitive silver halide emulsion and at least a 40percent excess of an image dye-providing color coupler based oneffective silver, comprising the steps of 1 developing said photographicelement in the presence of an aromatic primary amino color-developingagent and 2) contacting said element with an amplifier composition whichcomprises a cobalt(III) metal complex, an alkali metal bromide at aconcentration of from 2 g. to 40 g./l., an organic developmentrestrainer at a concentration of from 0.01 to 2 g./l., and wherein saidamplifier composition contains less than 30 percent by weight of thesilver halide solvent which would be necessary to fix said silver halideemulsion.

38. A process according to claim 37 wherein said image dye-providingcouplers are water-insoluble couplers dissolved in a coupler solvent.

39. A process according to claim 37 wherein one of said imagedye-providing layer units comprises a cyan dye-providing coupler andanother of said image dyeproviding layer units comprises a magentadyeproviding coupler and each of said layer units comprises said silverhalide emulsion at a concentration of less than 30 mg./ft.

40. A process according to claim 37 wherein each of said imagedye-providing layers contain a 110 percent stoichiometric excess of saidimage dye-providing color coupler.

7 3 UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No.2.766.891 Dated October 16, 1913 InventorKeQ William Blair Travis It iscertified that error appears in the above-identified patent and thatsaid Letters Patent are hereby corrected as shown below:

[Column 5, line 2, "r0" should read --for--. Column 7, lines 33:1

3%, "exposue exposure" should read --exposure to--; line #6, "metalic"should read --metallic-. Column 8, line 6, "inert" should read--"inert". Column 9, line 37, that part of formula reading "P- shouldread p- Column 13, line 33, that part of formula reading "ditert" shouldread di-tert ----5 line #6, under the word "stabilize", -dryshould beinserted; line 55, after "NahEDTA", should be inserted. Column 16, lines5 L- 55, "apprently apparently" should read --apparently carried-.Column 18, line 12, that art of formula reading "10" should read -[a-.Column 20, line 3, "p'ersent" should read "percent"; line 62, "where"should read -wherein--. Column 22, line 38, "contain" should read--contains-.--.

Signed and sealed this 24th day of September 1974.

(SEAL) Attest:

McCOY M. GIBSON JR. 0. MARSHALL DANN Attesting Officer Commissioner ofPatents

2. A process according to claim 1 wherein said color-developing agent isan aromatic primary amino compound.
 3. A process according to claim 1wherein said color-developing agent is imbibed in said photographicelement before contact with said amplifier composition.
 4. A processaccording to claim 1 wherein said development restrainer is abenzotriazole compound.
 5. A process according to claim 1 wherein saidphotographic element is developed in an aqueous developer bathcomprising a silver halide developing agent before contact with saidamplifier composition.
 6. A process according to claim 5 wherein saidsilver halide developing agent is a primary aromatic amino compound. 7.A process according to claim 5 wherein said developer contains at leasttwo silver halide developing agents which comprise a primary aromaticamino compound and at least one other compound which is ablack-and-white silver halide developing agent.
 8. A process accordingto claim 5 wherein said silver halide developing agent is ablack-and-white silver halide developing agent.
 9. A process accordingto claim 1 wherein said photographic element comprises at least two ofsaid color-providing layer units.
 10. A process according to claim 9wherein each of said color-providing layer units comprises said colorcoupler in at least a 40 percent stoichiometric excess based oneffective silver.
 11. In a process of developing an imagewise-exposedphotographic element comprising a support and at least one imagedye-providing layer unit thereon which contains a light-sensitive silverhalide emulsion having associated therewith a color coupler, theimprovement comprising development of the imagewise-exposed silverhalide emulsion to provide an imagewise distribution of metallic silverand imbibition of a color-developing agent in said photographic element,and then contacting said photographic element with an amplifiercomposition which contains a development resTrainer in a concentrationsufficient to repress substantially additional net silver developmentand wherein said amplifier solution contains a cobalt(III) metal complexhaving a coordination number of 6 and said amplifier solution ismaintained in contact with said photographic element under conditionswhich reduce said cobalt(III) to cobalt(II) and in turn oxidize saidcolor-developing agent to provide an increase in dye density with dyeproduced from said coupler in the areas corresponding to the imagewisedistribution of said metallic silver.
 12. A process according to claim11 wherein said amplifier bath contains a sufficient quantity ofdevelopment restrainer to repress substantially any further net silverdevelopment.
 13. A process according to claim 11 wherein saidcolor-developing agent imbibed in said photographic element is anaromatic primary amino compound.
 14. A process according to claim 11wherein said development of the imagewise-exposed silver halide emulsionis carried out in a liquid which is substantially free of cobalt (III)metal complex salts.
 15. A process according to claim 11 wherein saidamplifier bath is substantially free of silver halide solvents orcontains less than 30 percent by weight of the silver halide solventwhich would be necessary to fix a silver halide emulsion.
 16. A processaccording to claim 11 wherein the photographic element is developed insolution and contacted with an amplifying bath which is maintained attemperatures of above 90* F.
 17. A process according to claim 11 whereinsaid color-providing layer unit in said photographic element contains asilver halide emulsion in concentrations of up to 30 mg. of silver persquare foot.
 18. A process according to claim 11 wherein saidphotographic element is a multicolor photographic element comprising atleast two color-providing layer units which each contains a silverhalide emulsion having associated therewith a photographic color couplerin at least a 40 percent stoichiometric excess based on silver.
 19. Aprocess according to claim 11 wherein said photographic element is aphotographic element comprising at least one image dye-providing layerunit which contains a silver halide emulsion having associated therewitha water-insoluble image dye-providing coupler dissolved in a couplersolvent wherein said coupler is present in at least a 40 percentstoichiometric excess based on effective silver.
 20. A process accordingto claim 18 wherein each of said color-providing layer units contains asilver halide emulsion at a concentration of less than 30 mg. of silverper square foot.
 21. A process according to claim 11 wherein the halideconcentration of all silver halide emulsions in said element is lessthan 3 mole persent iodide.
 22. A process according to claim 12 whereinsaid development restrainer is substantially free of ionic iodide groupsand free mercapto groups.
 23. A process according to claim 12 whereinsaid development restrainer is the combination of from 0.01 to 2 g./l.of a benzotriazole and from 2 g. to 40 g./l. of an alkali metal bromide.24. A process according to claim 11 wherein said amplifier bath containsfrom 2 g. to 40 g. of an alkali metal bromide.
 25. A process accordingto claim 11 wherein said cobalt(III) metal complex is a cobalt hexamminesalt.
 26. A process according to claim 11 wherein said color-developingagent is 4-amino-N-ethyl-N-(2-methoxyethyl)-m-toluidinedi-p-toluenesulfonate.
 27. A process according to claim 11 wherein saidamplifier bath contains a coupling accelerator which is an alcohol. 28.A process according to claim 11 where development of said silver halideemulsion is carried out in a bath which contains a coupling acceleratorwhich is an alcohol.
 29. A process according to claim 11 wherein thehalide of the silver halide emulsion in said element is less than 0.25mole percent iodide.
 30. A process according to claim 11 wherein saidimagewise-exposed silver halide emulsion is developed in the presence ofa black-and-white developing agent.
 31. A process according to claim 11wherein said imagewise-exposed silver halide emulsion is developed inthe presence of an aromatic primary amino compound and at least oneother compound which is a black-and-white silver halide developingagent.
 32. A process for developing an imagewise-exposed photographicelement comprising a support having at least one layer unit thereonwhich contains a silver halide emulsion which has associated therewithat least a 40 percent stoichiometric excess of an image dye-formingcolor coupler based on silver, which process comprises 1) a developmentstep wherein said photographic element is developed to form an imagewisedistribution of silver and an aromatic primary amino color-developingagent is imbibed in said photographic element, and then 2) contactingsaid photographic element with an amplifier bath containing a) a cobalt(III) metal complex having a coordination number of 6 and b) adevelopment restrainer for sufficient time to produce image dye inaddition to any dye produced in said development step.
 33. A process forproviding or intensifying an image record in an imagewise-exposedphotographic element comprising a support having thereon at least oneimage dye-providing layer unit which contains a light-sensitive silverhalide emulsion and a dye image-providing coupler in at least a 40percent excess based on effective silver, comprising the steps of 1)developing said photographic element in the presence of an aromaticprimary amino color-developing agent and 2) contacting said element withan amplifier composition which comprises a cobalt(III) metal complex, analkali metal bromide at a concentration of from 2 g. to 40 g./l., anorganic development restrainer at a concentration of from 0.01 to 2g./l., and wherein said amplifier composition contains less than 30percent by weight of the silver halide solvent which would be necessaryto fix said silver halide emulsion.
 34. A process according to claim 33wherein the temperature of the amplifier composition is maintained atabove 100* F.
 35. A process according to claim 33 wherein saidcobalt(III) metal complex is cobalt hexammine.
 36. A process accordingto claim 33 wherein said image dye-providing layer unit contains saidcolor coupler in at least a 110 percent stoichiometric excess based oneffective silver.
 37. A process for providing or intensifying an imagerecord in an imagewise-exposed photographic element comprising a supporthaving thereon at least two image dye-providing layer units each ofwhich contains a light-sensitive silver halide emulsion and at least a40 percent excess of an image dye-providing color coupler based oneffective silver, comprising the steps of 1) developing saidphotographic element in the presence of an aromatic primary aminocolor-developing agent and 2) contacting said element with an amplifiercomposition which comprises a cobalt(III) metal complex, an alkali metalbromide at a concentration of from 2 g. to 40 g./l., an organicdevelopment restrainer at a concentration of from 0.01 to 2 g./l., andwherein said amplifier composition contains less than 30 percent byweight of the silver halide solvent which would be necessary to fix saidsilver halide emulsion.
 38. A process according to claim 37 wherein saidimage dye-providing couplers are water-insoluble couplers dissolved in acoupler solvent.
 39. A process according to claim 37 wherein one of saidimage dye-providing layer units comprises a cyan dye-providing couplerand another of said image dye-providing layer units comprises a magentadye-providing coupler and each of said layer units comprises said silverhalide emulsion at a concentration oF less than 30 mg./ft.2.
 40. Aprocess according to claim 37 wherein each of said image dye-providinglayers contain a 110 percent stoichiometric excess of said imagedye-providing color coupler.